The GitLab base-url needs to include the path to the API. For example
https://<base-url>/api/v4

Issue Token

To use Gitlab authentication, you can use your personal access token with scope api. You can use the following command to issue a token:

$ guard get token -o gitlab

Guard uses the token found in TokenReview request object to read user’s profile information and list of groups this user is member of. In the TokenReview response, status.user.username is set to user’s Gitlab login, status.user.groups is set to the list of the groups where this user is a member.